1. Field of the Invention
The present invention relates to a cooling structure for a heating element and a power converter.
2. Description of the Related Art
A power converter includes a circuit using semiconductor devices for performing current conduction and current blocking and provides functions of AC-DC conversion, frequency conversion, etc by controlling switching operations of the semiconductor devices. In the semiconductor devices in the power converter, losses are generated upon current conduction and switching during turning on and off. When a temperature of the semiconductor devices exceeds an operating limit point due to heat caused by the loss, current interruption cannot be done, so that the power converter cannot provide a desired operation. Accordingly, a cooling device for cooling the semiconductor devices is required in the power converter.
There are various types of semiconductor devices depending on an exterior, an electric characteristic, etc. Accordingly the cooling device is designed in accordance with respective characteristics. For example, JP 2013-73964 A discloses a semiconductor unit including a cooling device having two cooling surfaces, an electric terminal part, and a cooling unit with protrusions has a pin-shape.
JP 2000-060106 A discloses, similarly to JP 2013-73964 A, a cooling device including a high heat conductor, and an air-cooling fins on two cooling surfaces.
In addition, JP 2013-73964 A discloses, at a paragraph 0001, “the document relates to a power module having a high heat radiation characteristic and a high reliability and, at a paragraph 0011, “On one of the two confronting surfaces with larger area, is provided with a heat radiation part, and another surface has a heat radiation part”. The heat radiation parts function as heat radiation walls for a module case 304. On an outer circumferential surface, a plurality of fins are uniformly formed.
In JP 2013-73964 A, a cooling water is used for cooling the semiconductor devices. However, it is necessary to additionally provide a water channel, a pump, and a heat radiator separately. In addition, the power module housing the semiconductors therein has two surfaces for cooling the heat from their inside, each having a heat radiation part having a lot of fins on each of the surfaces, which may cause the structure to be complicated.
In JP 2000-060106 A, an increase in the cooling characteristic has been tried by arranging a heat radiator near the semiconductor devices, etc. However, the structure becomes complicated. Accordingly, when this structure is applied to a power converter requiring a lot of power modules, a size of the power converter becomes large.
On the other hand, there is a need to use as an air-cooling type one the heating element such as the semiconductor module having originally designed as a water-cooling type. This is because the use of the air-cooling type one eliminates necessity of piping for the coolant, which is advantageous to maintenance. When the air-cooling type is adopted, it becomes necessary to provide cooling fins, etc. having a certain size on the heating element. However, the heating element, originally having designed as a water-cooling type one, has small pin fines (fins protruding in a pin shape), etc. However, such a heating element is designed without assumption that a large pressurizing force is applicable, so that there is no assumption that a strong pressure force is applied. Accordingly, when an external cooling fin is simply mounted by fastening bolts, the heating element may be damaged.
An aspect of the present invention is to provide a cooling structure for a heating element or a plurality of power modules with extensibility in arranging the heating elements such as a power module and with down-sizing a device for power converters, etc., using the heating elements such as a plurality of power modules.
An aspect of the present invention is to provide a cooling structure for a heating element, having pin fins and being capable of cooling the heating element for a semiconductor module, etc with avoidance of damage and a power converter.